The invention relates generally to the field of repairing gas turbine components that have experienced corrosion damage. More specifically, the invention relates to methods that extend component life by reducing or eliminating further corrosion damage which would cause the component to be scrapped.
Gas turbine engine components, such as fan cases and gearboxes, are typically constructed of aluminum and magnesium alloys. These alloys are susceptible to corrosion due to exposure to the environment during regular service in the field. For example, damage can be caused due to the presence of water or moisture on the fan exit outer case. In addition, environmental conditions such as chemical fallout, saltwater, and others can exacerbate corrosion. The corrosion deteriorates the component's parent material and reduces its wall thickness. In some instances, the component's wall thickness is reduced to the point where the component cannot be repaired.
Current turbine component repair methods allow for dimensional restoration of aluminum and magnesium structures using a variety of techniques such as epoxy bonding, plasma spray, high velocity oxygen fuel (HVOF) thermal spray, fusion welding, and others. High temperature repair techniques such as fusion welding may result in unacceptable component distortion and degrade the substrate material properties by over-aging or solutioning. Epoxy bonding can break or spall during service, allowing the environmental elements to attack the underlying parent material. Subsequent attacks on the parent material will deteriorate wall thickness such that the component must be scrapped.
What is desired is a method of repairing gas turbine components that have suffered corrosive deterioration by identifying and mitigating the corrosion attack before the component wall thickness has deteriorated below minimum strength requirements, and restoring the original component dimensions while offering added corrosion protection.